Prostaglandin D2(PGD2) is a metabolic product of arachidonic acid through PGG2 and PGH2, and known to have various potent physiological activities. For example, in non-patent literature 1 it is described that PGD2 is involved in sleeping and secretion of hormones in central nervous system, and in inhibiting activity of platelet aggregation, contraction of bronchial smooth muscle, vasodilation and constriction of a blood vessel etc. in peripheral system. Moreover, PGD2 is considered to be involved in forming pathological condition of an allergic disease such as bronchial asthma since it is a major metabolic product of arachidonic acid produced from a mast cell, and has a potent bronchoconstricting effect, causing an increase of blood vessel permeability and migration of inflammatory cell such as an eosinophil.
A DP receptor (also called DP1 receptor) or CRTH2 receptor (also called DP2 receptor) is known as a receptor of PGD2 but these are completely different receptors. In Patent literatures 1-9 indole derivatives having a DP receptor antagonistic activity is disclosed, and in Patent literatures 10-21 indole derivatives having a CRTH2 receptor antagonistic activity is disclosed
Also, indole derivatives having inhibitory activity against noradrenaline re-uptake are disclosed in Patent literature 22.
Patent literature 1: WO 2005/056527 Pamphlet
Patent literature 2: WO 2004/111047 Pamphlet
Patent literature 3: WO 2004/103970 Pamphlet
Patent literature 4: WO 2004/039807 Pamphlet
Patent literature 5: WO 2003/062200 Pamphlet
Patent literature 6: WO 2002/094830 Pamphlet
Patent literature 7: WO 2001/079169 Pamphlet
Patent literature 8: WO 2003/022814 Pamphlet
Patent literature 9: WO 2003/022813 Pamphlet
Patent literature 10: WO 2003/097598 Pamphlet
Patent literature 11: WO 2003/097042 Pamphlet
Patent literature 12: WO 2005/019171 Pamphlet
Patent literature 13: WO 2004/106302 Pamphlet
Patent literature 14: WO 2004/007451 Pamphlet
Patent literature 15: WO 2003/101981 Pamphlet
Patent literature 16: WO 2003/101961 Pamphlet
Patent literature 17: WO 2003/066047 Pamphlet
Patent literature 18: WO 2005/040112 Pamphlet
Patent literature 19: WO 2005/040114 Pamphlet
Patent literature 20: WO 2005/044260 Pamphlet
Patent literature 21: GB 2407318A Pamphlet
Patent literature 22: WO 2005/019208 Pamphlet
Non-patent literature 1: Pharmacol. Review, Vol. 46, page 205-229 (1994)